Marking photographic paper.



R. s. BECKER.

MARKING PHOTOGRAPHIC PAPER. APPLICATION FILEDIUNE22.1915.

Patented Jan. 2,1917.

Fgwi

WITNESSES:

76115 A TTORNE Y5 U lll ET EEARKING: ?HOTOGRAPHI6 PAPER.

exact description thereof, reference being 'had to the accompanyingdrawing and to the reference-numerals marked thereon.

My present invention relates to photography and more particularly tophotographic paper and it has for its object to provide a method ofplacing identifying nature that they will not be obtrusive or, in fact,easily discernible but, on the other hand, quite invisible by eitherreflected or transmitted light, except under certain conditions, so thatordinarily paper bearing the mark will have the usual blank appearance.

A further ob ect is to so mark the paper that it willnot interfere inany way with the photographic properties thereof.

To these and other ends the invention resides in certain improvementsand combinationsof parts all as will be hereinafter more fullydescribed, the novel features being pointed out in the claims at the endof the specification.

Tn the drawings: Figure 1 is a plan View of the reverse side of a sheetof photographic paper marked in accordance with this invention, the markbeing invisible from this point oi view; 2 is a perspective view of thesheet showing the same side of the paper as viewed from an angle atwhich the mark becomes visible, and Fig. 3 is a sectional view of thesheet. 4

Similar reference numerals throughout the several figures indicate thesame parts.

It has been found desirable to place an identification mark onphotographically sensitized paper as a means, for instance, ofdistinguishing a particular brand from other similar brands, whereby theuser thereof may know as to its characteristics and so that it will bediiiicult for a commercial photographer who makes prints for the amateurto substitute another paper for the one called for. The thicker papers,such as post cards, may have black ink printing applied on their backs.but this method is not usable with the lighter Weights of paper, for onereason because of the mark fipccification of Letters Patent,

Application filed June 22, 1915.

marks upon the body of the paper of such a,

ii atented it $61.13 il 3 0. 716. n 1

showing through in the finished picture. Furthermore, the user ofphotographic paper is'likely to object to advertising marks appearingboldly on the rear of the paper, even if it does not show through. Forlike reasons, Water marks, being thin spots in the paper, are consideredobjectionable.

The object of my invention, as before stated, is to mark the back ofphotographic paper in such a manner that the mariflng will not bevisible on the face or objectionably noticeable on the back thereof, ande material used will not affect the sensitive emulsion.

Tn ordinary printing operations, an ink is preferred which gives themaximum contrast with the color of the paper. Accord to my method, Tprint the paper with an ink which so matches the hack of the paper incolor, as to be substantially invisible on the opposite side of thepaper from the printing, and only visible on the same side by reflectedlight, which passes from the paper to the eye within a given angularrange. Furthermore, this ink used for printing the designation on thepaper is of such a chemical nature it will not injuriously affect thesensitive emulsion on the other side of the paper or that of anotherpaper placed in contact with it in the pack.

In the drawings, T have shown in 1 a plan view of a sheet of ordinaryphotographic paper that has been marked in accordance with my inventionand which comprises a paper backing or base 1 on the front of which isthe sensitized body or layer of photographic emulsion. Looking directlyat the sheet with the line of vision at right angles to the plane of thepaper, as in 1, the mark is invisible, but when the sheet is tiltedbefore the eye with the light coming from the far side so that the angleof incidence is acute, the mark becomes visible, as shown in Fig. 2,providing the eye is in proper alinement at the similar angle ofrefiection. This is because the inked surface or the area covered by theimpression gives a distinguishably different optical reflection from thesurrounding plain paper surface. The mark shown in the present instanceis a combination of the letters ODA indicated requiremerits heretoforementioned, as for to its having an ink for use with ordinary paper maycomprise: barium sulfate, casein, formaldehyde, water, coloring matter.

The barium sulfate serves as a whitener; the casein as a"binder, and theformaldehyde as a hardener to render the mixture insoluble. Practicallyany suitably colored dyestuff may be used to give the ink the samegeneral color as that of the paper. While, theoretically, the dye shouldbe such as not to have any effect upon the emulsion, yet as a matter offact, such a small amount of the dye is present, that no deleteriouseffe'cts would be perceived with the use of any of the ordinary dyes onthe average types of paper.

The various ingredients of this ink may obviously be replaced by theirequivalents for the purpose specified. For example, the casein might bereplaced by gelatin, or any other suitable hardener to render the inkinsoluble might be substituted for the formaldehyde. With white paper,ordinary white inks may be used to advantage by adding coloring matterto them, provided the ink has such characteristics that a mark made'withit is substantially invisible from the opposite side of the paper, andnot glaringly or evenreadily noticeable on the same side as theprinting, due

substantially the same color as the paper, and which will not materiallyaffect the sensitized emulsion. It, of course, will be understood thatthe designation may be applied to the paper by using any of the wellknown printing appliances such as stamps, pr nting presses and the like,care being taken not to leave an impression in relief due to too heavypressure. The desing mark on the rear face,

ignation applied on the paper \may obviously be any suitable word,expression, picture or trade-mark.

By the term ink as used herein, I intend to cover any substance ormixture of substances that can be applied to paper to give a reasonablypermanent record of a desired marking without injuring the paper.

I claim as my invention:'

1. A photographically sensitized paper having an identifying markthereon, com prising a paper of a given color, a sensitized emulsion on'the front face and a designatsaidmark comprising a non-abrasive coloredink which is about the same color as the rear face of the paper and doesnot injuriously affect the emulsion, said mark being substantiallyinvisible through the paper, and not readily noticeable on the same sidethereof.

2. A photqgraphically sensitized paper having. an identifyingdesignation on the back thereof comprising a thin paper of a givencolor, a sensitized emulsion on the front face and a printed mark on-theback face, comprising a non-abrasive mixture of light colored ink andcoloring matter, which does not injuriously affect. the sensitizedemulsion, the .mark being of substantially the same color as the back ofthe paper, practically invisible from the front face of the paper andvisible from the rear only by reflected light viewed within a limitedangular range.

REINHOLD S. BECKER.

